1. Field of the Invention
The present invention relates to a multi-piece rim used for off-road wheels, for example, large and very large wheels for construction vehicles, and more particularly, relates to a fretting preventing structure for a lock ring groove of the multi-piece rim.
2. Description of the Prior Art
FIG. 3 illustrates the structure of a conventional multi-piece rim and FIG. 4 illustrates an enlarged cross-section of a portion of the multi-piece rim. As illustrated in FIGS. 3 and 4, the multi-piece rim includes a gutter band 1 which has a lock ring groove 6 and an O-ring groove 7, a lock ring 2 which has a slit in the circumferential direction and is mounted in the lock ring groove 6, a bead seat band 3 mounted onto the gutter band 1 and axially supported by the lock ring 2, a side ring 4 mounted onto the bead seat band 3 and axially supported by the bead seat band 3, and an O-ring 5 located at the O-ring groove 7.
The lock ring groove 6 includes a bottom surface 6a, side surfaces 6b, and curved surfaces 6c connecting the bottom surface 6a and the side surfaces 6b.
The conventional multi-piece rim has the following problems.
More particularly, when the multi-piece rim is mounted to a construction vehicle and is driven, contact pressure and relative sliding repeatedly occur at the contact surfaces between the members including the gutter band 1, the lock ring 2, the bead seat band 3 and the side ring 4. As a result, fretting is caused in the contact surfaces, and cracks are initiated and then develop into large cracks. When the cracks penetrate the entire thickness of the wall, the rim will cause fracturing.
Especially, as illustrated in FIGS. 4 and 5, the transition point from the axially outboard curved surface 6c to the axially outboard side surface 6b of the lock ring groove 6 formed in the gutter band 1 and a portion adjacent to the transition point (especially, a portion in the curved surface 6c) are repeatedly brought into contact with the lock ring 2 and repeatedly receive a load from the lock ring 2 in direction A (a radially inwardly and axially outboard direction). As a result, the transition point and the portion adjacent to the transition point will cause small cracks d which will develop into large cracks c (FIG. 6). When the cracks finally penetrate the full thickness of the gutter band 1, the gutter band 1 will be broken.